’RADIATION SICKNESS’

This is the response to whole-body radiation delivered over 48 hours or less.

Figure 59.3: THE EXPECTED FALL OUT PATTERN after a one–megaton surface burst on Mombasa, assuming a uniform southeasterly wind of 30 km/hr. The contours indicate seven day accumulated doses of 900, 300, and 90 rads to unprotected people. A dose of 500 rads will kill about half of those exposed to it.

0 to 100 rads. Men lose fertility at 20 to 50 rads

100 to 200 rads. After 3 to 6 hours there is nausea and vomiting which lasts for less than a day. After a latent period of up to 2 weeks, symptoms recur for 4 weeks. Leucopenia develops.

There are few deaths below 200 rails.

200 to 600 rads. Nausea and vomiting lasting 1 to 2 days are followed by the recurrence of symptoms for up to 8 weeks.

There is severe leucopenia, purpura, and haemorrhage, often with infection. Above 300 rads the hair is lost.

The death rate is 0 to 90% in 2 to 12 weeks from haemorrhage or infection.

600 to 1000 rads. Nausea and vomiting start within half an hour and last 2 days. There is a latent phase of 5 to 10 days, followed by the same symptoms as with 200 to 600 rads which last 1 to 4 weeks.

The death rate is 90 to 100% in 6 weeks from haemorrhage and infection.

1000 to 5000 rads. Nausea and vomiting start within half an hour and last one day. A latent phase of under 7 days is followed by fever and diarrhoea lasting 2 to 14 days. Everyone dies within 14 days from circulatory collapse.

More than 5000 rads. Almost immediate nausea and vomiting are followed by convulsions, tremor, ataxia, and lethargy.

Everyone dies within 48 hours from respiratory failure or cerebral oedema.

Anyone within 1.5 km of a 1 megaton bomb could expect to receive a dose of the initial radiation with a 50% chance of killing him (about 500 rads)—should he survive the initial heat and blast.

The dose from fallout decays exponentially by a factor of 10 for every sevenfold increase in time. If it is 3000 roentgens per hour at one hour, it will be 300 at 7 hours; at 49 hours (77) it will be only 30 roentgens an hour. In practice, radiation from fallout is difficult to calculate, and has to be measured. Here is an example. After a one megaton ground burst with a uniform wind of 24 km an hour, the fallout plume that would expose an unprotected person to a fatal cumulative dose (about 500 rads) in the first week after the explosion would be 240 km long and 32 km wide.

The longer the fission products remain in the mushroom cloud, the less radioactive they will be when they fall to the ground. They are likely to arrive in dangerous concentrations for at least 24 hours. If you are in the path of the plume, there will be an interval before the fallout arrives, which will depend on your distance from ground zero and on the wind speed. When it first arrives, the dose rate is small. It then builds up over a day or two and decays.

Whereas there is little effective protection from the heat and blast, except perhaps in a deep bunker, some protection is possible from the fine radioactive dust of the fallout.